ports/unix: add LWIP_UNIX_ANDROID to LWIP_ERRNO_STDINCLUDE=1 branch (h…

…eiher#4)

On Android, Bionic libc defines 'errno' as a macro that expands to a
function call ('(*__errno())'). Combined with LWIP's 'LWIP_ERRNO_INCLUDE
<errno.h>' define, the preprocessor substitutes the 'errno' token inside
'<errno.h>' before the '#include' directive is processed, producing
invalid '<(*__errno()).h>' and fatal 'file not found' error.

Linux, HURD and KFreeBSD already set LWIP_ERRNO_STDINCLUDE=1 so that
errno.h is included directly via '#include <errno.h>' (without going
through LWIP_ERRNO_INCLUDE macro indirection). Android's libc has the
same issue and benefits from the same fix.

Repro before patch (NDK r27+/r30-beta1, API 28+):
    third-part/lwip/src/include/lwip/errno.h:188:10: fatal error:
    '(*__errno()).h' file not found
    #include LWIP_ERRNO_INCLUDE
             ^~~~~~~~~~~~~~~~~~
    /src/ports/unix/include/cc.h:55:28: note: expanded from macro
    'LWIP_ERRNO_INCLUDE'
    #define LWIP_ERRNO_INCLUDE <errno.h>

After patch: compiles cleanly on Android for all three ABI
(arm64-v8a, armeabi-v7a, x86_64). Discovered building
heiher/hev-socks5-tunnel on NDK r30.

CI: Add FreeBSD checker

CI: Switch to using the distro's LLVM.

CI: Update musl-cross to 20250520.

UDP: Fix use after free when PCB is freed.

Sync to v2.2.1.

CI: Allow build to be triggered manually.

SIO: Fix compile warnings.

Ports: Fix byte order.

CI: Add mips{el}-unknown-linux-muslsf targets.